TM_THURSDAY
result->tm_wday = (result->tm_wday + TM_THURSDAY) % DAYSPERWEEK;
{ "Thursday", TM_THURSDAY },
{ "last-Thursday", TM_THURSDAY },
EPOCH_WDAY = TM_THURSDAY
result->tm_wday = (result->tm_wday + TM_THURSDAY) % DAYSPERWEEK;
#define EPOCH_WDAY TM_THURSDAY